Insulated resistor



y 1942- A. HABERBERGER 2,282,651

INSULATED RESISTOR Filed Feb. 28, 1941 Patented May 12, 1942 INSULATED RESISTOR Anthony Habcrberger, St. Marys, Pa., assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Application February 28, 1941, Serial No. 381,030

4 Claims.

This invention relates to electrical resistors, and more particularly to insulated fixed resistors and a method of making them.

At present most small fixed resistors, such as used in radios, are made from a cylindrical body of resistance material from which terminals or leads project, and many of them have a cylindrical coating or covering of insulating material. Insulation of the ends of the resistor bodies always presents a problem in manufacture and added expense, so most of them do not have in sulated ends. In case the resistors have flexible terminals or leads embedded in their ends from which they project axial v, flexing of the terminals when connecting a resistor in a circuit often causes them to break close to the resistor body due to the bending being sharp and more or less localized at that point. Also, the portion of a terminal molded in the resistor is apt to be flexed and thereby cause the resistor body to crack. In an effort to overcome these difficulties the terminals have been strengthened inside of and adjacent the ends of the resistor body so that bending will occur farther out and be distributed over a greater length of the wire. This does not entirely solve the problems, and it requires special preparation of the terminals.

It is among the objects of this invention to provide an insulated fixed resistor which has uninsulated but protected ends, in which no special treatment of the terminals is necessary in order to preventthem from being broken off, and in which the resistors insulation materially reduces the likelihood of the terminals breaking off next to the resistor body. Another object is to provide a method for making such a resistor in an easy and inexpensive manner.

In accordance with this invention a resistor body is provided with an insulated covering that extends beyond its ends which remain bare. The ends are thus protected to a large extent by the surrounding ring of insulation from accidentally making contact with an outside conductor. The resistor is generally provided with flexible terminals that project axially from its ends. The insulating sleeve projects far enough beyond the ends of' the resistor body to materially decrease the distance that the portions of the terminals adjacent the body can be bent away from the axis of the body whereby to restrict the bending of those portions to an angle which does not cause the terminals to break off near the body nor to crack it. That is. after a terminal engages the projecting end of the insulating sleeve its inner end portion can not bend farther.

Therefore further bonding is conl'incd to the outer portion of the terminal. The body and sleeve are molded separately and not baked, but depend upon the natural cohesion of the particles from which they are made to hold them together. The body is then inserted in the sleeve and the unit thus formed is baked to cure it. The sleeve is preferably made from a thermo-setting resin which shrinks onto the resistor body when cured. Also, during the curing stage some of the resin at the engaging surfaces of the body and sleeve unites so that the sleeve is firmly bonded to the body.

The preferred embodiment of the invention is illustrated in the accompanying drawing in which Fig. 1 is a side view, partly in section, of a resistor body with terminal wire leads embedded in'its ends; Fig. 2 is a side view of a resistor insulated in accordance with my invention with the insulation partly broken away; Fig. 3 is a view similar to Fig. 2 showing one of the terminal wires bent to the side; and Fig. 4 is an end view of the insulated resistor.

Referring to Fig. 1, a cylindrical resistor body I is cold molded from a mixture of powdered bonding material and an electrical conductor, preferably a polymerizable resin and graphite. The headed inner ends of flexible wire terminals 2 are embedded in the ends of the body from which the terminals project substantially axially. The resistor body shown in this figure has not been baked, but there is sufiicient natural cohesion between its component particles to render it self-sustaining when handled with reasonable care.

As shown in Fig. 2, a cylindrical tube or sleeve 3 having an internal diameter substantially no larger than the diameter of the resistor body I is molded from a thermo-setting insulating material, preferably a polymerizable resin. This sleeve likewise is only cold molded at first, but it is strong enough to permit the resistor body to be inserted in it as shown. The assembled sleeve and body are then baked to cure them and to cause the sleeve to shrink onto the body so that they are held rigidly together. At the same time the bond between them is strengthened by the uniting of a small amount of resin at their engaging surfaces.

Another feature of this invention is that the sleeve 3 is materially longer than the resistor body, and the latter is placed substantially midway between the ends of the sleeve so thatthey project an appreciable distance beyond the ends of the body. The ends of the body are thus protected from accidental contact with any outside conductor that is not inserted in the ends of the sleeve. A stated above, the ends of the sleeve project an appreciable distance beyond the ends of the resistor body, by which is meant far enough to materially shorten the distance that the portion of either terminal adjacent the body can be bent, so that the terminal will not be bent beyond its elastic limit at that point and broken, and will not crack the resistor. Thus, as shown in Fig. 3, when a terminal is bent it strikes the projecting end or the insulation sleeve before it has bent more than about 45 from the-axis of the resistor, whereupon the inner end portion of the terminal can be bent no farther. Any further bending occurs at the point of engagement between terminal and sleeve and outwardly beyond that point. Consequently, when the outer portion of a terminal is bent at right angles two spaced 45 angles are formed in the terminal instead of one 90 angle close to the end of the resistor body. The bending istherefore not only decreased at any one point along the terminal, but it is distributed throughout a greater length of it.

It willthus be seen that a resistor constructed in accordance with this invention has its ends protected in a simple and inexpensive manner. In addition, the chance of breaking the terminals or cracking the resistor body is greatly reduced and in a manner that does not require special terminals.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A resistor element comprising a body of resistance material, a flexible terminal projecting from an end thereof, the exposed portion of said terminal having substantially the same flexibility throughout its length whereby the terminal will bend at the body, and an insulating covering on said body projecting an appreciable distance beyond said end and outwardly along the terminal far enough to materially restrict the distance that the portion or said terminal adjacent the body can be bent away from the axis of the body.

2. A resistor element comprising a body of resistance material, a flexible terminal wire embedded therein and the body, the exposed portion of the wire having substantially the same flexibility throughout its length whereby the wire will bend at the body, and a rigid insulating covering on said body projecting from said end an appreciable distance whereby to materially restrict the distance the portion of said terminal wire adjacent said body can be bent away from the axis of the body.

3. A resistor element comprising a body of resistance material, an embedded flexible terminal projecting axially from each end thereof, the exposed portion of each of the terminals having substantially the same flexibility throughout its length whereby the terminal will bend at the body, and a rigid insulating sleeve mounted on said body and projecting an appreciable and substantially equal distance beyond both ends of the body and outwardly along the terminals far enough to materially restrict the distance that the portions of said terminals adjacent the body can be bent away from the axis of the body.

4. A resistor element comprising a heat cured resistor body formed of a mixture of powdered polymerizable resin and electrical conducting material, a, flexible terminal embedded in each end of said body and projecting axially therefrom, the exposed portion of each of the terminals having substantially the same flexibility throughout its length whereby the terminal will bend at the body, and a surrounding rigid insulating sleeve formed of a thermo-setting polymerizable resin tightly engaging said body throughout its length, said sleeve projecting an appreciable and substantially equal distance beyond both ends of the body and outwardly along the terminals far enough to materially restrict the distance that the portions of said terminals adjacent the body can be bent away from the axis of the body, and some of the resin in the inner surface of the sleeve .being fused with resin in the adjoining surface of the body whereby to form a firm bond between body and sleeve.

ANTHONY HABERBERGER.

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